How to switch the ac phase not the neutral

Thread Starter

Mostafa Elhabrok

Joined Nov 5, 2015
11
i have a single phase ac motor, and i have 3 apartments each one uses a different phase.
i want to run this motor from every apartment by standard switch.
the problem if two switches are closed at the same time, i have two phases shorten .
i wanted to use a triac but i realized that it controls the neutral side (because of the common ground and using the gate )
i want to control the PHASE side of each phase of the three.
 

BR-549

Joined Sep 22, 2013
4,940
“i want to run this motor from every apartment by standard switch.”

Do you need to ONLY activate the motor from each apartment by chance?.......just turn on?

Or do you need complete, separate control from each apartment?
 

Alec_t

Joined Sep 17, 2013
10,432
The disadvantage of using a triac (or SSR with a triac output stage) is that it can fail either open circuit or short circuit. If the latter, then you could have two phases shorted. Can you arrange to power the motor from only one phase, but use the switches just to provide input signals to a controller for the motor?
 

recklessrog

Joined May 23, 2013
985
I would be safer to use relays as there is less chance of them failing short circuit like semiconductors can. All you need then is to have a simple Phase monitor control that senses whether there is power to the motor and will not allow another phase to be turned on until the others are off.
We controlled 4.5kV 6 phase windings on massive motors like that back in the late 60's early 70's.
 

Thread Starter

Mostafa Elhabrok

Joined Nov 5, 2015
11
“i want to run this motor from every apartment by standard switch.”

Do you need to ONLY activate the motor from each apartment by chance?.......just turn on?

Or do you need complete, separate control from each apartment?
every apartment has its switch, what i need is that every apartment is able to run the motor from its phase without two phases shorten.
as if two switches are closed at the same time that will be a short circuit between different phases
 

Thread Starter

Mostafa Elhabrok

Joined Nov 5, 2015
11
I would be safer to use relays as there is less chance of them failing short circuit like semiconductors can. All you need then is to have a simple Phase monitor control that senses whether there is power to the motor and will not allow another phase to be turned on until the others are off.
We controlled 4.5kV 6 phase windings on massive motors like that back in the late 60's early 70's.
that is a good idea but i did not prefer relays as they are slower , and depend on mechanical parts
 

Thread Starter

Mostafa Elhabrok

Joined Nov 5, 2015
11
The disadvantage of using a triac (or SSR with a triac output stage) is that it can fail either open circuit or short circuit. If the latter, then you could have two phases shorted. Can you arrange to power the motor from only one phase, but use the switches just to provide input signals to a controller for the motor?
the problem is that the motor is running alot , and every apartment its own power meter ( cost )
 

MaxHeadRoom

Joined Jul 18, 2013
19,162
If you want each apartment to pay their individual cost, what happens if the demand is from 2 or 3 apartments and the same motor is used?
Max.
 

Thread Starter

Mostafa Elhabrok

Joined Nov 5, 2015
11
i appreciate everyone's help
but on my condition is there any digital way to control the 3 phases as the following
when
apartment #1 closes its switch then its phase is connected to the motor while the other two phases are disconnected
and #2 and #3 like the same
 
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